Sensing and feedback for the formation of complex three-dimensional acoustic fields

ABSTRACT

An apparatus includes a precursor dispenser for dispensing a precursor material into a workspace, one or more acoustic sources configured to direct acoustic waves towards the workspace to provide acoustic fields that arrange the precursor material in a three-dimensional shape in the workspace, one or more sensors configured to detect a distribution of the precursor material in the workspace, and an electronic controller in communication with the precursor dispenser, the one or more acoustic sources, and the one or more sensors, the electronic controller being programmed to cause the one or more acoustic sources to adjust the acoustic fields to reduce deviations in the distribution of the precursor material from the three-dimensional shape in the workspace.

TECHNICAL FIELD

The disclosure relates to acoustic holography systems that can includesensing and feedback features.

BACKGROUND

Acoustic holography systems use acoustic waves to produce acousticfields in a workspace. These acoustic fields can create one or moreenergy extrema that can interact with a medium in the workspace. Bycontrolling the acoustic fields produced by the acoustic waves, anacoustic holography system can assemble the medium into a desiredpattern to produce an acoustic hologram.

Typically, acoustic holography systems use one or more arrays ofacoustic transducers to produce a desired acoustic hologram in theworkspace. In some cases, an acoustic holography system can use acombination of an acoustic transducer and a fixed acoustic diffractivedevice, such as an acoustic hologram plate, to produce a desiredacoustic hologram. The hologram plate is manufactured to diffractincoming acoustic waves from the acoustic transducer to produce a seriesof diffracted waves. These diffracted waves can interfere with oneanother to produce a particular acoustic field in the workspace in orderto assemble the workspace medium into the desired pattern.

SUMMARY

Acoustic holography systems are typically used to create 2D orrelatively simple 3D acoustic holograms due to the complexity ofproducing more advanced acoustic fields. For example, in systems thatuse one or more arrays of acoustic transducers to produce a desiredacoustic hologram, the number of transducers tends to increase with thecomplexity of the hologram, making complex designs challenging due topractical constraints. Acoustic hologram plates can allow for morecomplex acoustic fields without the need for large transducer arrays.However, these plates are designed to produce a particular field, andthus must be replaced to produce a new field. In either case, suchconventional approaches are unable to identify and reduce deviationsfrom a desired acoustic field using, for example, a variable hologramplate and/or feedback principles.

Various aspects of the present disclosure are summarized as follows.

In general, in an aspect, the present disclosure features an apparatusincluding a precursor dispenser for dispensing a precursor material intoa workspace, one or more acoustic sources configured to direct acousticwaves towards the workspace to provide acoustic fields that arrange theprecursor material in a three-dimensional shape in the workspace, one ormore sensors configured to detect a distribution of the precursormaterial in the workspace, and an electronic controller in communicationwith the precursor dispenser, the one or more acoustic sources, and theone or more sensors, the electronic controller being programmed to causethe one or more acoustic sources to adjust the acoustic fields to reducedeviations in the distribution of the precursor material from thethree-dimensional shape in the workspace.

Implementations of the apparatus can include one or a combination of twoor more of the following features and/or features of other aspects.

The one or more acoustic sources can include an array of transducers.The one or more acoustic sources can include at least one transducer incombination with an acoustic diffractive device.

The acoustic diffractive device can be a variable acoustic diffractivedevice. The variable acoustic diffractive device can include anelectrorheological fluid and an array of electrodes arranged toindependently provide an electric field to a corresponding portion ofthe electrorheological fluid in response to signals from the electroniccontroller.

The variable acoustic diffractive device can include a non-Newtonianfluid and an array of actuators arranged to independently provide amechanical stress to a corresponding portion of the non-Newtonian fluidin response to signals from the electronic controller.

The variable acoustic diffractive device can include two or moremicrofluidic channels and a pump arranged to move a fluid into or out ofa selected microfluidic channel in response to signals from theelectronic controller.

The apparatus can include a curing device configured to cure theprecursor material in the workspace in response to signals from theelectronic controller. The curing device can include a radiation sourceor a reagent source. The electronic controller can be programmed tocause the curing device to cure the precursor material in the workspacein response to determining that the deviations in the distribution ofthe precursor material from the three-dimensional shape are less than apredetermined threshold.

The acoustic fields can include one or more energy extrema sufficient totrap the precursor material in the three-dimensional shape in theworkspace.

The apparatus can include a chamber enclosing the workspace.

In general, in an aspect, the present disclosure features a methodincluding directing acoustic waves toward a workspace to arrange aprecursor material in a three-dimensional shape in the workspace,determining, using one or more sensors, a distribution of the precursormaterial in the workspace, and adjusting the acoustic waves to reducedeviations in the distribution of the precursor material from thethree-dimensional shape in the workspace.

Implementations of the method can include one or a combination of two ormore of the following features and/or features of other aspects.

The method can include curing at least a portion of the precursormaterial in the workspace in response to determining that the deviationsin the distribution of the portion of the precursor material from thethree-dimensional shape are less than a predetermined threshold.

The acoustic waves can be provided by an array of transducers. Theacoustic waves can be provided by at least one transducer in combinationwith an acoustic diffractive device.

The acoustic diffractive device can be a variable acoustic diffractivedevice. The variable acoustic diffractive device can include anelectrorheological fluid and an array of electrodes arranged toindependently provide an electric field to a corresponding portion ofthe electrorheological fluid in response to signals from an electroniccontroller.

The variable acoustic diffractive device can include a non-Newtonianfluid and an array of actuators arranged to independently provide amechanical stress to a corresponding portion of the non-Newtonian fluidin response to signals from an electronic controller.

The variable acoustic diffractive device can include two or moremicrofluidic channels and a pump arranged to move a fluid into or out ofa selected microfluidic channel in response to signals from anelectronic controller.

In general, in an aspect, the present disclosure includes a 3D printingsystem including a precursor dispenser for dispensing a precursormaterial into a workspace, the precursor material being curable uponexposure to a curing agent, a curing device positioned to supply thecuring agent to the workspace, one or more acoustic sources fordirecting acoustic waves towards the workspace such that the acousticwaves provide acoustic fields to arrange the precursor material in athree-dimensional shape in the workspace, one or more sensors fordetecting a distribution of the precursor material in the workspace, andan electronic controller in communication with the precursor dispenser,the curing device, the one or more acoustic sources, and the one or moresensors, the electronic controller being programmed to supply signals tocause the one or more acoustic sources to adjust the acoustic fields toreduce deviations in the distribution of the precursor material from thethree-dimensional shape in the workspace and supply signals to cause thecuring device to cure at least a portion of the precursor material inthe workspace in response to determining that the deviations in thedistribution of the portion of the precursor material from thethree-dimensional shape are less than a predetermined threshold.

Among other advantages, the present disclosure can provide for avariable acoustic diffractive device that can enable an acousticholography system to dynamically control the acoustic fields itproduces. This can allow the system to create arbitrary 2D or 3Dacoustic holograms without the need for large transducer arrays.Moreover, the variable acoustic diffractive device can enable the systemto change the acoustic field without the need to manufacture a newacoustic hologram plate. The techniques described here can also enablean acoustic holography system to identify deviations from a desiredacoustic field and correct them in real time.

Other advantages will be apparent from the description below and theclaims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of an acoustic holography system inaccordance with one embodiment.

FIGS. 2A, 2B, and 2C are schematic diagrams of a variable acousticdiffractive device in accordance with one embodiment.

FIG. 3 is a schematic diagram of a variable acoustic diffractive devicein accordance with another embodiment.

FIG. 4 is a schematic diagram of an acoustic holography system inaccordance with another embodiment.

FIG. 5 is a flowchart of a process for generating an acoustic hologramin a medium in accordance with one embodiment.

FIG. 6 is a flowchart of a process for generating a three-dimensionalshape in a workspace in accordance with one embodiment.

FIG. 7 is a schematic diagram of a computer system that can be used withor form part of the foregoing embodiments.

Like reference numbers and designations in the various drawings indicatelike elements.

DETAILED DESCRIPTION

Acoustic holography systems are disclosed that include a variableacoustic diffractive device having one or more diffractive elements withindependently controllable acoustic properties. By varying the acousticproperties of the diffractive elements, the system can dynamicallycontrol the acoustic fields it produces in a workspace in order tomanipulate a medium in the workspace. Also disclosed are acousticholography systems having a sensor unit that can identify thedistribution of the medium in the workspace. The sensor unit can feedthis information back to the system to enable the system to correct fordeviations from the desired distribution in real time.

FIG. 1 illustrates an acoustic holography system 100 that includes anacoustic assembly 102 for generating acoustic waves 104 within aworkspace 106. As the acoustic waves 104 propagate within the workspace106, they produce acoustic fields that can interact with a medium in theworkspace 106. By controlling the acoustic waves 104, the acousticholography system 100 can produce acoustic fields that can assemble orotherwise manipulate the medium into desired positions within theworkspace 106 in order to, for example, produce a desiredtwo-dimensional or three-dimensional pattern. The term “pattern” as usedherein includes any two-dimensional or three-dimensional arrangement,structure, or other formation and is not limited to formations that aresymmetric or that repeat in a predictable manner.

For example, in some implementations, the acoustic holography system 100can generate acoustic waves 104 that produce an acoustic field having apredetermined acoustic pressure and phase distribution in a certainplane 110 of the workspace 106. The acoustic pressure and phasedistribution can create nodes that force the medium to assemble into adesired two-dimensional acoustic hologram 108 in the plane 110 of theworkspace 106. In some implementations, the acoustic holography system100 can generate acoustic waves 104 that produce predetermined acousticpressure and phase distributions across multiple planes 110 to assemblethe medium into a desired three-dimensional acoustic hologram 112 in theworkspace 106. In some cases, the acoustic holography system 100 can beconfigured to vary the acoustic waves 104 to dynamically adjust theacoustic pressure and phase distributions in real time, for example, toreconfigure, move, rotate, or otherwise manipulate the medium or otherobjects within the workspace 106.

In general, the medium in the workspace 106 can be any gas, liquid, orsemisolid medium, or a medium formed from a mixture of one or moregases, liquids, and/or solids. For example, in some implementations, themedium can include a precursor material, such as plastic particles,polymer particles, metal particles, glass particles, ceramic particles,wood particles, composite particles, metamaterial particles, or othersolid or liquid particles, mixed with a liquid or gas. In some cases,the medium can include one or more objects, such as biological cells,suspended in a liquid or gas. In some implementations, the medium caninclude a mixture of two or more gases, liquids, or solids having thesame or similar densities to facilitate suspension and manipulation ofthe medium and its individual components.

Acoustic holography system 100 includes a dispenser 114 for dispensingthe medium into the workspace 106 in response to signals from anelectronic controller 116. The electronic controller 116 can include oneor more processors and non-transitory storage media coupled withelectronic signaling hardware to produce the signals that control thedispenser 114 and other components of the acoustic holography system100. The dispenser 114 may be configured to control the size and shapeof the medium and its individual components to ensure consistentoperation of the acoustic holography system 100. The acoustic holographysystem 100 also includes a receptacle 118 to contain the medium withinthe workspace 106. In some cases, the receptacle 118 is coupled with anactuator 120 configured to vary the position of the receptacle 118 alongone or more dimensions in response to signals from the electroniccontroller 116. In doing so, the electronic controller 116 varies therelative position between the acoustic assembly 102 and the workspace106.

In order to generate the acoustic waves 104 within the workspace 106,the acoustic assembly 102 includes an acoustic source 122. The acousticsource 122 can include one or more transducers, such as a piezoelectrictransducer or another acoustic transducer. In some implementations, theacoustic source 122 can include an array of individually addressabletransducers or a phased array transducer. Moreover, in some cases, theacoustic holography system 100 can include multiple acoustic sources 122and/or acoustic assemblies 102 arranged at different positions aroundthe workspace 106.

Each of the transducers within the acoustic source 122 can be coupledwith the electronic controller 116 and can be configured to generateacoustic waves at one or more amplitudes, phases, and/or frequencies inresponse to signals from the electronic controller 116. In general, theacoustic source 122 can be configured to operate at any frequency. Insome implementations, the acoustic source 122 can operate at ultrasonicfrequencies (i.e., frequencies above approximately 20 kHz) so that theacoustic waves it generates are above the upper audible limit of humanhearing.

In some implementations, the acoustic source 122 can generate acousticwaves 104 that produce a desired acoustic pressure and phasedistribution within the workspace 106 without the need for anyintervening acoustic elements. For example, the electronic controller116 can calculate the transducer inputs that generate a set of acousticwaves that can interfere to produce a desired acoustic pressure andphase distribution in a particular plane 110 for a given workspace 106medium. In some cases, the electronic controller 116 can perform such acalculation across multiple planes 110 to determine a set of acousticwaves that produce a desired three-dimensional acoustic pressure andphase distribution in the workspace 106. The electronic controller 116can then control the amplitude, phase, and/or frequency of thetransducers within the acoustic source 122 to generate the set ofacoustic waves and produce the desired acoustic pressure and phasedistribution.

The acoustic assembly 102 includes an acoustic diffractive device 124positioned between the acoustic source 122 and the workspace 106. Theacoustic diffractive device 124 can include one or more diffractiveelements 126 configured to diffract incoming acoustic waves generated bythe acoustic source 122. The acoustic properties of each of thediffractive elements 126 can be selected to alter the phase and/oramplitude of the incoming acoustic waves to produce diffracted acousticwaves in the workspace 106. These diffracted acoustic waves canself-interfere to form the acoustic waves 104 that produce a desiredacoustic pressure and phase distribution in the workspace 106.

For example, in some implementations, the desired acoustic pressure andphase distribution in the workspace 106 can be converted into a seriesof phase and/or amplitude shifts that can be applied by the acousticdiffractive device 124. Such a calculation can be carried out by, forexample, the electronic controller 116 using an angular spectrumalgorithm, a Gerchberg-Saxton algorithm, or any other inversediffraction algorithm. The calculation can also account for thefrequency of the incoming acoustic waves from the acoustic source 122,the acoustic properties of the medium within the workspace 106, andgravitational forces, among others. One or more acoustic properties,such as the acoustic impedance, of each diffractive element 126 can beselected to apply the calculated phase and/or amplitude shift to theincoming acoustic waves in order to produce the desired acousticpressure and phase distribution in the workspace 106. The acousticproperties of each diffractive element 126 can be selected, for example,by selecting the thickness of the diffractive element (e.g., thethickness along the z-axis in FIG. 1) and/or by selecting the materialof the diffractive element, among others.

By including the acoustic diffractive device 124 in the acousticassembly 102, the acoustic holography system 100 can produce asymmetricacoustic pressure and phase distributions in the workspace 106. Further,the acoustic holography system 100 can achieve greater precision and canexert finer control over the distribution than in implementations whereonly an acoustic source is used. Moreover, the system can produce thedesired acoustic pressure and phase distribution using a singletransducer instead of relying on multiple transducers which may reducesystem cost and complexity.

As shown in FIG. 1, in some implementations, the acoustic diffractivedevice 124 can be in contact with the acoustic source 122 or otherwisein the near-field of the acoustic source 122. In other implementations,the acoustic diffractive device 124 can be positioned at a distance fromthe acoustic source 122 such that it is in the far field of the acousticsource 122.

In some implementations, the surface dimensions of the acousticdiffractive device 124 can be sized to match the surface dimensions ofthe acoustic source 122. Although the acoustic source 122 and theacoustic diffractive device 124 are depicted as having a generallyrectangular surface, other arrangements, such as a circular surface, areequally compatible with the techniques described here.

In general, the acoustic diffractive device 124 can be a transmissivediffractive device or a reflective diffractive device. In someimplementations, one or more transmissive and/or reflective diffractivedevices can be combined to create the acoustic diffractive device 124.

In some implementations, the acoustic diffractive device 124 can be afixed acoustic diffractive device, such as a holographic plate,configured to produce a particular acoustic pressure and phasedistribution in the workspace 106. Such a device can be manufactured,for example, from a plastic or another acoustically transmissivematerial using techniques such as 3D printing or injection molding,among others. The fixed acoustic diffractive device can be replaceablewithin the acoustic holography system 100 to enable the system toproduce different acoustic pressure and phase distributions as desired.In some implementations, the fixed acoustic diffractive device 124 canbe configured to produce different acoustic pressure and phasedistributions, for example, in response to different frequency wavesfrom the acoustic source 122 or by employing the principle ofholographic redundancy.

In some implementations, the acoustic diffractive device 124 can be avariable acoustic diffractive device. The variable acoustic diffractivedevice can include one or more independently controllable diffractiveelements configured to adjust their acoustic properties in response tosignals from the electronic controller 116. This in turn enables theelectronic controller 116 to dynamically adjust the acoustic pressureand phase distribution in the workspace 106 in real time without theneed to manufacture a new acoustic diffractive device.

FIGS. 2A-C illustrate a variable acoustic diffractive device 200 inaccordance with one embodiment of the present disclosure. The variableacoustic diffractive device 200 includes a fluid chamber 202 dividedinto an array of sub-chambers 210. Each sub-chamber 210 includes wallsthat define the boundaries of an individually controllable diffractiveelement 212. Moreover, each sub-chamber 210 contains anelectrorheological (ER) fluid 206 whose apparent viscosity changes inresponse to an electric field. The fluid chamber 202 is positioned abovean electrode array 204 such that each sub-chamber 210 of the fluidchamber 202 is associated with one or more electrodes 208 of theelectrode array 204. Each electrode 208 can be individually addressableby the electronic controller 116, for example, to allow the electroniccontroller 116 to apply a selected voltage to each individual electrode208. The variable acoustic diffractive device 200 also includes a commonground electrode 214 positioned at a distance from the electrode array204.

By applying a voltage to one or more of the electrodes 208 in theelectrode array 204, the electronic controller 116 can create anelectric field within a corresponding sub-chamber 210 of the fluidchamber 202. This in turn changes the viscosity of the ER fluid 206within the sub-chamber 210. For example, FIG. 2B illustrates thevariable acoustic diffractive device 200 having ER fluid 206 with auniform viscosity in the absence of an electric field in any of thesub-chambers 210, and FIG. 2C illustrates the variable acousticdiffractive device 200 having an increased viscosity ER fluid 214 inresponse to an electric field in some of the sub-chambers 210, withdarker shading representing higher viscosity ER fluid 214. This changein viscosity can produce a corresponding change in the acousticproperties of the ER fluid 206, such as the acoustic impedance of thefluid and/or the speed of sound in the fluid in the presence ofboundaries. Thus, by adjusting the voltage applied to each of theelectrodes 208, the electronic controller 116 can dynamically change theacoustic properties of the diffractive elements 212 in the variableacoustic diffractive device 200. In this way, the electronic controller116 can configure the variable acoustic diffractive device 200 to applya predetermined phase and/or amplitude shift to the incoming acousticwaves from the acoustic source 122 in order to produce a desiredacoustic pressure and phase distribution in the workspace 106. Theresultant acoustic pressure and phase distribution can assemble orotherwise manipulate the medium into desired positions within theworkspace 106 in order to, for example, produce an acoustic hologram orreconfigure, move, rotate, or otherwise manipulate the medium within theworkspace 106.

Various modifications to the variable acoustic diffractive device 200are possible. For example, in some implementations, the variableacoustic diffractive device 200 may not include a common groundelectrode 214 and may instead use the electrodes 208 in the electrodearray 204 or another electrode array to define the electric field.Moreover, in some implementations, the fluid chamber 202 may not bedivided into an array of sub-chambers 210. In some cases, one or morewalls of each sub-chamber can be electrically conductive to create oneor more electrodes 208 used to produce the electric field within thesub-chamber. Although the electrode array 204 is depicted as containinga specific number of electrodes 208, the variable acoustic diffractivedevice 200 can generally include any number of electrodes 208 in theelectrode array 204. Similarly, although the fluid chamber 202 isdepicted as containing a specific number of sub-chambers 210, the fluidchamber 202 can generally be divided into any number of sub-chambers210. In some cases, the electrodes 208 and/or the sub-chambers 210 canbe arranged to form a 3D array of independently controllable diffractiveelements.

In some implementations, the variable acoustic diffractive device 200can include a non-Newtonian fluid combined with the ER fluid 206. Insuch a case, the electronic controller 116 can cause the acoustic source122 to transmit acoustic waves at a high frequency to increase theviscosity of the non-Newtonian fluid. This feature can be useful inorder to lock-in or freeze the configuration of the fluids in thevariable acoustic diffractive device 200, for example, after the deviceis configured to produce a desired acoustic pressure and phasedistribution in the workspace 106. In doing so, the electroniccontroller 116 can reduce power consumption (e.g., by cutting offvoltage to the electrodes 208 in the electrode array 204) and can avoidinaccuracies in the desired acoustic pressure and phased distributionthat may be caused by variations in the electric field during operation.To change the configuration of the variable acoustic diffractive device200, the electronic controller 116 can cause the acoustic source 122 tostop transmitting or to transmit acoustic waves at a low frequency toreturn the non-Newtonian fluid to its normal viscosity state.

In some implementations, a non-Newtonian fluid can be used in place ofthe ER fluid 206. In this case, the electrode array 204 can be used toform an array of individually addressable electrostatic actuators (orcan be replaced with another array of individually addressableactuators, such as mechanical or hydraulic actuators, among others).Each actuator can be arranged to independently provide a mechanicalstress to a corresponding portion of the non-Newtonian fluid in responseto the signals from the electronic controller 116. By adjusting themechanical stress applied by one or more of the actuators, theelectronic controller 116 can dynamically change the acoustic propertiesof a corresponding diffractive element in the modified variable acousticdiffractive device. In this way, the electronic controller 116 canconfigure the device to apply a predetermined phase and/or amplitudeshift to the incoming acoustic waves from the acoustic source 122 inorder to produce a desired acoustic pressure and phase distribution inthe workspace 106.

In some implementations, the ER fluid 206 (or the fluid chamber 202) canbe combined with or replaced by an electroactive polymer that exhibits achange in size or shape in response to an electric field. By adjustingthe voltage applied to each of the electrodes 208, the electroniccontroller 116 can cause the electroactive polymer to deform todynamically change the acoustic properties of the diffractive elementsin the modified variable acoustic diffractive device. In this way, theelectronic controller 116 can configure the variable acousticdiffractive device to apply a predetermined phase and/or amplitude shiftto the incoming acoustic waves from the acoustic source 122 in order toproduce a desired acoustic pressure and phase distribution in theworkspace 106.

In some implementations, the fluid chamber 202 can be deformed todynamically change the acoustic properties of the variable acousticdiffractive device 200. For example, in some cases, some or all of thechamber 202 can be formed from an elastomer, such as an elastomericdielectric, or another flexible material. In some cases, the chamber 202can be a solid component (that is, without an internal cavity for the ERfluid 206). In some cases, the chamber 202 (which may or may not includethe sub-chambers 210) can contain the fluid 206, which may include or bereplaced by a liquid or solid dielectric material. By adjusting thevoltage applied to each of the electrodes 208, the electronic controller116 can cause each electrode 208 to actuate a predetermined distancetowards the ground plane 214 or a corresponding electrode of anotherelectrode array on the opposite side of the chamber 202 as theelectrodes 208. In this way, the electronic controller 116 can cause thefluid chamber 202 to selectively deform (which can displace andpressurize the fluid 206, if included within the chamber 202) todynamically change the acoustic properties of the diffractive elementsin the variable acoustic diffractive device.

FIG. 3 illustrates a variable acoustic diffractive device 300 inaccordance with another embodiment of the present disclosure. Thevariable acoustic diffractive device 300 includes a series ofmicrofluidic channels 302 and at least one pump 304 arranged to move afluid 308 into or out of a selected microfluidic channel 302 in responseto signals from the electronic controller 116. In general, the variableacoustic diffractive device 300 can include any number of microfluidicchannels 302. In some implementations, the variable acoustic diffractivedevice 300 can include multiple layers of microfluidic channels stackedon top of one another, as shown in FIG. 3. Moreover, the variableacoustic diffractive device 300 includes one or more reservoirs 306 tohold a particular fluid 308 as it is moved into and out of amicrofluidic channel 302. Although the variable acoustic diffractivedevice 300 can generally include any fluid 308, in some implementations,the fluids 308 may be selected based on one or more of their acousticproperties, such as their density or acoustic impedance.

The variable acoustic diffractive device 300 can be configured todiffract incoming waves from the acoustic source 122 to produce adesired acoustic pressure and phase distribution in the workspace 106.For example, the electronic controller 116 can obtain informationregarding the acoustic properties of each fluid 308, and can move one ormore of the fluids 308 into or out of a selected microfluidic channel302 to alter the phase and/or amplitude of the incoming acoustic waves.In this way, the electronic controller 116 can produce a desiredacoustic pressure and phase distribution in the workspace 106 in orderto assemble or otherwise manipulate the medium or other objects in theworkspace 106.

In some implementations, each pump 304 included in the variable acousticdiffractive device 300 can be a mechanical pump, such as a pressurepump, a syringe pump, a peristaltic pump, or any other mechanical pumpcapable of manipulating small volumes. In cases where a dielectric fluidis used, each pump 304 can be an electrohydrodynamic pump, such as anelectroosmotic pump.

Referring back to FIG. 1, in some implementations, the acousticholography system 100 can be a three-dimensional (3D) printing system.In such a case, the electronic controller 116 can cause the dispenser114 to dispense a medium containing a precursor material into theworkspace 106, and can configure the acoustic assembly 102 to generateacoustic waves 104 that produce a predetermined acoustic pressure andphase distribution within the workspace 106, as described above. Theacoustic pressure and phase distribution can assemble the precursormaterial into the desired 3D structure to be printed. The electroniccontroller 116 can then send signals to a curing device 128 to cause thedevice to emit a curing agent, such heat, ultraviolet (UV) light, or areagent, among others, in order to cure all of, or a selected sectionof, the assembled precursor material. For example, in some cases, theelectronic controller 116 can divide the 3D structure into one or moresections of arbitrary shape, and can cause the curing device 128 to curethe medium that forms each section. This process can be repeated untilall of the sections of the 3D structure are cured. In some cases, eachsection can be cured in a predetermined curing order determined by theelectronic controller 116 in order to, for example, minimize mechanicalstress in the resulting 3D structure and/or enable curing of a 3Dstructure whose geometry does not allow all in one curing due toshadowing, among others.

To print more complex 3D structures, or to print arbitrary 3D structureswith greater accuracy and precision, the acoustic holography system 100can include a variable acoustic diffractive device in the acousticassembly 102. In this case, the electronic controller 116 can break the3D structure into a series of two-dimensional (2D) images, and canconfigure the variable acoustic diffractive device to produce anacoustic pressure and phase distribution in a plane 110 of the workspace106 that corresponds to the first image in the series of 2D images. Theacoustic pressure and phase distribution can assemble the precursormaterial into the desired 2D image in the plane 110, and the electroniccontroller 116 can cause the curing device 128 to cure the assembledprecursor material. The electronic controller 116 can then adjust theacoustic properties of one or more diffractive elements in the variableacoustic diffractive device to produce a new acoustic pressure and phasedistribution in an adjacent plane 110 in the workspace 106 thatcorresponds to a second image in the series of 2D images. In some cases,the electronic controller 116 can use the actuator 120 to move theworkspace 106 in addition to or instead of reconfiguring the variableacoustic diffractive device. In either case, the newly formeddistribution can assemble the precursor material into the desiredpositions in the adjacent plane 110, and the electronic controller 116can cause the curing device 128 to cure the assembled precursor materialto the previously cured layer. This process can be repeated until thedesired 3D structure is formed.

FIG. 4 shows an acoustic holography system 400 in accordance withanother embodiment of the present disclosure. The acoustic holographysystem 400 can include one or more of the features and functions of theacoustic holography system 100. Thus, repetitive description of likeelements is omitted for the sake of brevity.

In general, the acoustic holography system 400 includes an electroniccontroller 116 configured to control an acoustic assembly 102 togenerate acoustic waves 104 that produce a desired acoustic pressure andphase distribution in the workspace 106. In some implementations, thedesired distribution can be produced directly by an acoustic source 122having an array of acoustic transducers (e.g., a phased arraytransducer) without any intervening acoustic elements. In otherimplementations, the distribution can be produced by a fixed or variableacoustic diffractive device configured to diffract incoming waves fromthe acoustic source 122. The acoustic pressure and phase distributioncan manipulate the medium in the workspace 106 to produce, for example,a desired two-dimensional or three-dimensional acoustic hologram.

Given the complexity of producing the desired acoustic pressure andphase distribution in the workspace 106, as well as the circular effectthat a change in the workspace 106 can have on the intendeddistribution, it may be desirable to allow for feedback within theacoustic holography system. Accordingly, the acoustic holography system400 includes a sensor unit 402 configured to monitor the distribution ofthe medium within the workspace 106 in real time. The sensor unit 402can include one or more sensors, such as an image sensor, an ultrasoundsensor, a computed tomography sensor, a micro-CT sensor, an opticaltomography sensor, an infra-red (IR) sensor, or a LIDAR sensor, amongothers. Each sensor in the sensor unit 402 can provide informationregarding the distribution in the workspace 106 to the electroniccontroller 116 in real time.

The electronic controller 116 can use the information received from thesensor unit 402 to reduce deviations in the acoustic pressure and phasedistribution within the workspace 106. For example, the electroniccontroller 116 can compare the intended medium distribution 404 (e.g.,as defined by the intended 2D or 3D hologram structure) with the actualmedium distribution 406 (e.g., as defined by the information receivedfrom the sensor unit 402) to determine the differences. The electroniccontroller 116 may then apply one or more optimization algorithms todetermine which amplitude, phase, and/or frequency adjustments can bemade to reduce the differences and improve the distribution. In somecases, the electronic controller 116 can use one or more machinelearning or pattern recognition algorithms to determine whichadjustments are most appropriate to reduce the differences. In someimplementations, the electronic controller 116 can apply one or morethresholds to the difference information to determine whether anadjustment to the distribution should be made.

After identifying one or more adjustments to the distribution, theelectronic controller 116 can configure the acoustic assembly 102 toapply the adjustments. In some implementations, the electroniccontroller 116 can apply the adjustments by altering the amplitude,phase, and/or frequency of one or more transducers within the acousticsource 122. The electronic controller 116 can also apply the adjustmentsby dynamically altering the acoustic properties of one or morediffractive elements in the variable diffractive device. In this way,the acoustic holography system 400 can identify and correct deviationsin an intended acoustic pressure and phase distribution in real timethrough adjustments to the acoustic assembly 102.

For instance, in some implementations, the acoustic holography system400 can be a 3D printing system. Rather than printing a 3D structureusing a series of 2D layers as described above, the acoustic holographysystem 400 can produce a complex 3D acoustic pressure and phasedistribution within the workspace 106. The acoustic holography system400 can then use the feedback provided by the sensor unit 402 to reduceany deviations in the distribution until a precursor material includedin the medium is arranged in the 3D structure with a desired level ofaccuracy. The acoustic holography system 400 can then cause a curingdevice 128 to cure all of, or a selected section of, the precursormaterial to produce the 3D structure. In doing so, the acousticholography system 400 may print the 3D structure with greater speedand/or accuracy than the layer-by-layer approach.

In some cases, the electronic controller 116 can divide the 3D structureinto one or more sections of arbitrary shape, and can cause the curingdevice 128 to cure the medium that forms each section until all of thesections of the 3D structure are cured. For example, the electroniccontroller 116 may use the feedback provided the sensor unit 402 todetermine that the medium is arranged within a desired level of accuracyfor a particular section of the 3D structure. The controller can thencause the curing device 128 to cure the precursor material in the mediumthat corresponds to the section of the 3D structure. The electroniccontroller 116 can also cause each section to be cured in apredetermined curing order calculated in order to, for example, minimizemechanical stress in the resulting 3D structure and/or enable curing ofa 3D structure whose geometry does not allow all in one curing due toshadowing, among others.

The acoustic holography systems described herein can also be applied invarious other contexts. For example, in some cases, the acousticholography system can be applied in the medical context for diagnostics,such as in elastography or other medical imaging, or for medicaltreatment, such as by manipulating biological cells or other objectswithin a person. In other cases, the acoustic holography system can beapplied to facilitate contactless power transfer, 2D or 3D imaging, 2Dor 3D visualization, provide haptic feedback, or to move voids,deviations, defects, grain boundaries, fibers, or other inhomogeneitieswithin a medium to a desired location, alignment, or pattern, or toremove them from the medium altogether.

FIG. 5 is a flowchart of a process 500 for generating an acoustichologram in a medium in accordance with one embodiment. At least aportion of the process 500 can be implemented using one or moreprocessors operating within the electronic controller 116. Operations ofthe process 500 include directing an acoustic wave to a variableacoustic diffractive device (502). In some implementations, the variableacoustic diffractive device includes an electrorheological fluid and anarray of electrodes arranged to independently provide an electric fieldto a corresponding portion of the electrorheological fluid in responseto signals from an electronic controller. In other implementations, thevariable acoustic diffractive device includes a non-Newtonian fluid andan array of actuators arranged to independently provide a mechanicalstress to a corresponding portion of the non-Newtonian fluid in responseto signals from an electronic controller. In other cases, the variableacoustic diffractive device includes two or more microfluidic channelsand a pump arranged to move a fluid into or out of a selectedmicrofluidic channel in response to signals from an electroniccontroller.

Operations of the process 500 also include diffracting the acoustic waveusing the variable acoustic diffractive device to provide a time-varyingdiffracted acoustic wave in a workspace (504). The workspace can be aplane or multiple planes. The acoustic forces from the diffractedacoustic wave in the workspace can cause a non-uniform distribution ofthe medium in accordance with a predetermined pattern.

The process 500 further includes subjecting the medium to thetime-varying diffracted acoustic wave in the workspace to providetime-varying non-uniform acoustic forces to generate the acoustichologram in the medium (506). In some implementations, the medium can bea precursor material curable upon exposure to a curing agent, such as aradiation source or a reagent source, and an electronic controller cancause a curing device to supply the curing agent to the workspace. Insome cases, the electronic controller can be programmed to cause thevariable acoustic diffractive device to vary the non-uniform acousticforces to move adjust the medium. In some cases, an imaging device canimage the workspace while the non-uniform acoustic forces are providedto the medium located in the workspace.

FIG. 6 is a flowchart of a process 600 for generating athree-dimensional shape in a workspace accordance with one embodiment.At least a portion of the process 600 can be implemented using one ormore processors operating within the electronic controller 116.Operations of the process 600 include directing acoustic waves toward aworkspace to arrange a precursor material in a three-dimensional shapein the workspace (602). In some implementations, the acoustic waves areprovided by an array of transducers. In other implementations, theacoustic waves are provided by at least one transducer in combinationwith an acoustic diffractive device, which may be a variable acousticdiffractive device. In some cases, the variable acoustic diffractivedevice can include an electrorheological fluid and an array ofelectrodes arranged to independently provide an electric field to acorresponding portion of the electrorheological fluid in response tosignals from an electronic controller. In other cases, the variableacoustic diffractive device can include a non-Newtonian fluid and anarray of actuators arranged to independently provide a mechanical stressto a corresponding portion of the non-Newtonian fluid in response tosignals from an electronic controller. In still other cases, thevariable acoustic diffractive device can include two or moremicrofluidic channels and a pump arranged to move a fluid into or out ofa selected microfluidic channel in response to signals from anelectronic controller.

Operations of the process 600 also include determining a distribution ofthe precursor material in the workspace using one or more sensors (604).In some implementations, the sensors can include at least one of anultrasound sensor, a computed tomography sensor, a micro-CT sensor, anoptical tomography sensor, an infra-red (IR) sensor, or a LIDAR sensor.

The process 600 further includes adjusting the acoustic waves to reducedeviations in the distribution of the precursor material from thethree-dimensional shape in the workspace (606). In some implementations,the electronic controller can cause a curing device to cure theprecursor material in the workspace in response to determining that thedeviations in the distribution of the precursor material from thethree-dimensional shape are less than a predetermined threshold. In somecases, curing device can be a radiation source or a reagent source.

Embodiments of the subject matter and the functional operationsdescribed in this specification can be implemented in digital electroniccircuitry, in tangibly-embodied computer software or firmware, incomputer hardware, including the structures disclosed in thisspecification and their structural equivalents, or in combinations ofone or more of them. Embodiments of the subject matter described in thisspecification can be implemented as one or more computer programs, i.e.,one or more modules of computer program instructions encoded on atangible non-transitory storage medium for execution by, or to controlthe operation of, data processing apparatus. The computer storage mediumcan be a machine-readable storage device, a machine-readable storagesubstrate, a random or serial access memory device, or a combination ofone or more of them. Alternatively, or in addition, the programinstructions can be encoded on an artificially-generated propagatedsignal, e.g., a machine-generated electrical, optical, orelectromagnetic signal that is generated to encode information fortransmission to suitable receiver apparatus for execution by a dataprocessing apparatus.

The term “data processing apparatus” refers to data processing hardwareand encompasses all kinds of apparatus, devices, and machines forprocessing data, including by way of example a programmable processor, acomputer, or multiple processors or computers. The apparatus can alsobe, or further include, special purpose logic circuitry, e.g., an FPGA(field programmable gate array) or an ASIC (application-specificintegrated circuit). The apparatus can optionally include, in additionto hardware, code that creates an execution environment for computerprograms, e.g., code that constitutes processor firmware, a protocolstack, a database management system, an operating system, or acombination of one or more of them. Data processing apparatus can beincorporated into or in communication with the electronic controllers,such as the electronic controller 116 described above.

A computer program, which may also be referred to or described as aprogram, software, a software application, an app, a module, a softwaremodule, a script, or code, can be written in any form of programminglanguage, including compiled or interpreted languages, or declarative orprocedural languages; and it can be deployed in any form, including as astand-alone program or as a module, component, subroutine, or other unitsuitable for use in a computing environment. A program may, but neednot, correspond to a file in a file system. A program can be stored in aportion of a file that holds other programs or data, e.g., one or morescripts stored in a markup language document, in a single file dedicatedto the program in question, or in multiple coordinated files, e.g.,files that store one or more modules, sub-programs, or portions of code.A computer program can be deployed to be executed on one computer or onmultiple computers that are located at one site or distributed acrossmultiple sites and interconnected by a data communication network.

The processes and logic flows described in this specification can beperformed by one or more programmable computers executing one or morecomputer programs to perform functions by operating on input data andgenerating output. The processes and logic flows can also be performedby special purpose logic circuitry, e.g., an FPGA or an ASIC, or by acombination of special purpose logic circuitry and one or moreprogrammed computers.

Computers suitable for the execution of a computer program can be basedon general or special purpose microprocessors or both, or any other kindof central processing unit. Generally, a central processing unit willreceive instructions and data from a read-only memory or a random accessmemory or both. The essential elements of a computer are a centralprocessing unit for performing or executing instructions and one or morememory devices for storing instructions and data. The central processingunit and the memory can be supplemented by, or incorporated in, specialpurpose logic circuitry. Generally, a computer will also include, or beoperatively coupled to receive data from or transfer data to, or both,one or more mass storage devices for storing data, e.g., magnetic,magneto-optical disks, or optical disks. However, a computer need nothave such devices. Moreover, a computer can be embedded in anotherdevice, e.g., a mobile telephone, a personal digital assistant (PDA), amobile audio or video player, a game console, a Global PositioningSystem (GPS) receiver, or a portable storage device, e.g., a universalserial bus (USB) flash drive, to name just a few.

Computer-readable media suitable for storing computer programinstructions and data include all forms of non-volatile memory, mediaand memory devices, including by way of example semiconductor memorydevices, e.g., EPROM, EEPROM, and flash memory devices; magnetic disks,e.g., internal hard disks or removable disks; magneto-optical disks; andCD-ROM and DVD-ROM disks.

To provide for interaction with a user, embodiments of the subjectmatter described in this specification can be implemented on a computerhaving a display device, e.g., a CRT (cathode ray tube) or LCD (liquidcrystal display) monitor, for displaying information to the user and akeyboard and a pointing device, e.g., a mouse or a trackball, by whichthe user can provide input to the computer. Other kinds of devices canbe used to provide for interaction with a user as well; for example,feedback provided to the user can be any form of sensory feedback, e.g.,visual feedback, auditory feedback, or tactile feedback; and input fromthe user can be received in any form, including acoustic, speech, ortactile input. In addition, a computer can interact with a user bysending documents to and receiving documents from a device that is usedby the user; for example, by sending web pages to a web browser on auser's device in response to requests received from the web browser.Also, a computer can interact with a user by sending text messages orother forms of message to a personal device, e.g., a smartphone, runninga messaging application, and receiving responsive messages from the userin return.

Embodiments of the subject matter described in this specification can beimplemented in a computing system that includes a back-end component,e.g., as a data server, or that includes a middleware component, e.g.,an application server, or that includes a front-end component, e.g., aclient computer having a graphical user interface, a web browser, or anapp through which a user can interact with an implementation of thesubject matter described in this specification, or any combination ofone or more such back-end, middleware, or front-end components. Thecomponents of the system can be interconnected by any form or medium ofdigital data communication, e.g., a communication network. Examples ofcommunication networks include a local area network (LAN) and a widearea network (WAN), e.g., the Internet.

The computing system can include clients and servers. A client andserver are generally remote from each other and typically interactthrough a communication network. The relationship of client and serverarises by virtue of computer programs running on the respectivecomputers and having a client-server relationship to each other. In someembodiments, a server transmits data, e.g., an HTML page, to a userdevice, e.g., for purposes of displaying data to and receiving userinput from a user interacting with the device, which acts as a client.Data generated at the user device, e.g., a result of the userinteraction, can be received at the server from the device.

An example of one such type of computer is shown in FIG. 7, which showsa schematic diagram of a generic computer system 700. The system 700 canbe used for the operations described in association with any of thecomputer-implemented methods described previously, according to oneimplementation. The system 700 includes a processor 710, a memory 720, astorage device 730, and an input/output device 740. Each of thecomponents 710, 720, 730, and 740 are interconnected using a system bus750. The processor 710 is capable of processing instructions forexecution within the system 700. In one implementation, the processor710 is a single-threaded processor. In another implementation, theprocessor 710 is a multi-threaded processor. The processor 710 iscapable of processing instructions stored in the memory 720 or on thestorage device 730 to display graphical information for a user interfaceon the input/output device 740.

The memory 720 stores information within the system 700. In oneimplementation, the memory 720 is a computer-readable medium. In oneimplementation, the memory 720 is a volatile memory unit. In anotherimplementation, the memory 720 is a non-volatile memory unit.

The storage device 730 is capable of providing mass storage for thesystem 700. In one implementation, the storage device 730 is acomputer-readable medium. In various different implementations, thestorage device 730 may be a floppy disk device, a hard disk device, anoptical disk device, or a tape device.

The input/output device 740 provides input/output operations for thesystem 700. In one implementation, the input/output device 740 includesa keyboard and/or pointing device. In another implementation, theinput/output device 740 includes a display unit for displaying graphicaluser interfaces.

While this specification contains many specific implementation details,these should not be construed as limitations on the scope of the presentdisclosure or on the scope of what may be claimed, but rather asdescriptions of features that may be specific to particular embodimentsof particular aspects of the present disclosure. Certain features thatare described in this specification in the context of separateembodiments can also be implemented in combination in a singleembodiment. Conversely, various features that are described in thecontext of a single embodiment can also be implemented in multipleembodiments separately or in any suitable subcombination. Moreover,although features may be described above as acting in certaincombinations and even initially be claimed as such, one or more featuresfrom a claimed combination can in some cases be excised from thecombination, and the claimed combination may be directed to asubcombination or variation of a subcombination.

Similarly, while operations are depicted in the drawings in a particularorder, this should not be understood as requiring that such operationsbe performed in the particular order shown or in sequential order, orthat all illustrated operations be performed, to achieve desirableresults. In certain circumstances, multitasking and parallel processingmay be advantageous. Moreover, the separation of various system modulesand components in the embodiments described above should not beunderstood as requiring such separation in all embodiments, and itshould be understood that the described program components and systemscan generally be integrated together in a single software product orpackaged into multiple software products.

A number of embodiments have been described. Other embodiments are inthe following claims.

What is claimed is:
 1. An apparatus, comprising: a precursor dispenserfor dispensing a precursor material into a workspace; one or moreacoustic sources configured to direct acoustic waves towards theworkspace through an acoustic diffractive device to provide acousticfields that arrange the precursor material in a three-dimensional shapein the workspace; one or more sensors configured to detect adistribution of the precursor material in the workspace; the acousticdiffractive device configured to alter the acoustic waves from the oneor more acoustic sources to provide altered acoustic fields; anelectronic controller in communication with the precursor dispenser, theone or more acoustic sources, the acoustic diffractive device, and theone or more sensors, the electronic controller being programmed to:determine, based on the distribution of the precursor material detectedby the one or more sensors and a predetermined threshold value, that atleast one deviation in the distribution of the precursor material fromthe three-dimensional shape in the workspace is larger than apredetermined threshold value; in response to determining that thedeviations are larger than the predetermined threshold, calculate, basedon feedback parameters including the distribution of the precursormaterial detected by the one or more sensors, one or more alteredacoustic field parameters; and controlling, based on the calculated oneor more altered acoustic field parameters, the acoustic diffractivedevice to dynamically adjust the acoustic fields to reduce the at leastone deviation in the distribution of the precursor material from thethree-dimensional shape in the workspace.
 2. The apparatus of claim 1,wherein the one or more acoustic sources comprise an array oftransducers.
 3. The apparatus of claim 1, wherein the one or moreacoustic sources comprise at least one transducer in combination with anacoustic diffractive device.
 4. The apparatus of claim 3, wherein theacoustic diffractive device is a variable acoustic diffractive device.5. The apparatus of claim 4, wherein the variable acoustic diffractivedevice comprises an electrorheological fluid and an array of electrodesarranged to independently provide an electric field to a correspondingportion of the electrorheological fluid in response to signals from theelectronic controller.
 6. The apparatus of claim 4, wherein the variableacoustic diffractive device comprises a non-Newtonian fluid and an arrayof actuators arranged to independently provide a mechanical stress to acorresponding portion of the non-Newtonian fluid in response to signalsfrom the electronic controller.
 7. The apparatus of claim 4, wherein thevariable acoustic diffractive device comprises two or more microfluidicchannels and a pump arranged to move a fluid into or out of a selectedmicrofluidic channel in response to signals from the electroniccontroller.
 8. The apparatus of claim 1, further comprising a curingdevice configured to cure the precursor material in the workspace inresponse to signals from the electronic controller.
 9. The apparatus ofclaim 8, wherein the electronic controller is programmed to cause thecuring device to cure the precursor material in the workspace inresponse to determining that the deviations in the distribution of theprecursor material from the three-dimensional shape are less than apredetermined threshold.
 10. The apparatus of claim 8, wherein thecuring device comprises a radiation source or a reagent source.
 11. Theapparatus of claim 1, wherein the acoustic fields comprises one or moreenergy extrema sufficient to trap the precursor material in thethree-dimensional shape in the workspace.
 12. The apparatus of claim 1,further comprising a chamber enclosing the workspace.
 13. A 3D printingsystem, comprising: a precursor dispenser for dispensing a precursormaterial into a workspace, the precursor material being curable uponexposure to a curing agent; a curing device positioned to supply thecuring agent to the workspace; one or more acoustic sources fordirecting acoustic waves towards the workspace such that the acousticwaves provide acoustic fields to arrange the precursor material in athree-dimensional shape in the workspace; one or more sensors fordetecting a distribution of the precursor material in the workspace; andan electronic controller in communication with the precursor dispenser,the curing device, the one or more acoustic sources, and the one or moresensors, the electronic controller being programmed to: determine, basedon the distribution of the precursor material in the workspace detectedby the one or more sensors, that the deviations are larger than apredetermined threshold; in response to determining that the deviationsare larger than the predetermined threshold, calculate one or morealtered acoustic field parameters; supply signals, based on thecalculated one or more altered acoustic field parameters, to cause theone or more acoustic sources to adjust the acoustic fields to reducedeviations in the distribution of the precursor material from thethree-dimensional shape in the workspace; and supply signals to causethe curing device to cure at least a portion of the precursor materialin the workspace in response to determining that the deviations in thedistribution of the portion of the precursor material from thethree-dimensional shape are less than a predetermined threshold.